c不等于0,且a,b,c,2b成等差数列,则a/c=?忘记怎么算?
a,b,c,2b成等差数列,则 2b=a+c......(1), b+2b=2c<===>3b=2c......(2). 由(1)得b=(a+c)/2代入(2)得3a=c, ∴ a/c=1/3.